The proposed studies continue our development of mycoplasma virology, concentrating on the enveloped mycoplasmavirus MVL2 and on MVL3, a mycoplasma-virus morphologically similar to T7 coliphage. These studies fall into four areas: (1) the continued analysis of MVL2 DNA replicaive intermediates during productive infection and in persistently infected cells, (2) the study of viral protein synthesis in MVL2 infected cells and structural relationships of the proteins in the MVL2 virion, (3) electron microscopic studies of the ultra structural events during MVL3 infection, and (4) attempts to isolate and charceterize MVL3 ts mutants and construct a genetic map of this virus.